Late animation deformity in the denervated pedicled latissimus dorsi flap.

Optimal management of the thoracodorsal nerve in pedicled latissimus dorsi flaps for mastectomy reconstruction is controversial. The incidence and etiology of animation deformity despite muscle denervation remain poorly- understood. This study examines the incidence, etiology, and risk factors of late animation. A retrospective review identified breasts reconstructed with a denervated pedicled latissimus dorsi flap. The incidence and severity of postoperative animation were examined with investigation of potential patient, oncologic, and reconstructive causative factors. Patients completed a survey to assess lifestyle implications. A cadaveric dissection identified anatomical causes of persistent muscle innervation. Forty-one reconstructions with a minimum follow-up of 2 years (average 6.25 years) identified no significant relationship between animation and patient or treatment factors. While absent in the first postoperative year, animation was identified in 90% of patients on long-term follow-up, with 32% reporting pain, and 25% indicating lifestyle interferences. This high frequency of animation correlated with cadaveric results that identified multiple extramuscular nerve branches innervating the latissimus in 9 of 10 specimens. The distance between nerve branches was 5.4 ± 0.7 mm, and the distance between the superior muscle margin and the branching point was 22.7 ± 2.3 mm. Persistent animation deformity, despite nerve transection, is attributable to anatomical differences in the thoracodorsal branching patterns, rather than patient or therapeutic factors. While early follow-up may suggest transection of a single nerve branch is adequate to prevent animation, our study demonstrates that long term, it is insufficient in most cases. Exploration for additional nerve branches or high division proximal to the branching site is suggested, and preoperative patient counseling is recommended.